The key hypothesis of this proposal holds that the connective tissue activation process, mediated by potent cytokines drives many of the events of inflammation, influencing both reparative (proliferative) and destructive mechanisms. We propose to define the manner in which the cytokine, CTAP-III, initiates and sustains connective tissue activation, and to define its pathogenetic roles in inflammation. Construction of recombinant CTAP-III molecules and synthetic peptides of both native and novel configuration offers opportunities to develop new tactics to influence key sites in the inflammatory process. Our ultimate goal is to devise agents or procedures which favorably modify inflammation in man, including suppressing the process (as in rheumatoid arthritis), and enhancing aspects of normal physiology (as in wound healing). Knowledge of the structure of connective tissue activating peptide-III (CTAP-III) is critical to understanding structure-function relationships through which this cytokine expresses its biological effects. To delineate CTAP-III structure-function relationships, we will determine the residues or sequences critical to the anabolic, chemotactic and other activities in normal, OA and rheumatoid synovial cell cultures. This will be accomplished: (1) by chemical modifications of CTAP-III, (2) by construction of relevant synthetic peptides, and (3) by site directed mutagenesis of recombinant CTAP-III. The direct structure-function studies will be extended by collaborative efforts to define the three dimensional structure of CTAP-III by X-ray crystallographic and Nuclear Magnetic Resonance studies. The mechanisms/s by which CTAP-III activates connective tissue cells will be clarified by receptor binding studies and definition of possible co- ligands critical to CTAP-III dependent connective cell activation. The roles of (1) CTAP-III binding to proteoglycans of cell membranes and extracellular matrix and putative heparanase activity, and (2) CTAP-III induction of cytokines in sustaining the activated state of normal, OA, and RA synovial cells will be studied to clarify the biologic basis of chronic inflammation.